November 2003

M0512-112603

MIC2042/2043

Micrel

MIC2042/2043

Single Channel, High Current, Low Voltage,

Protected Power Distribution Switch

General Description

The MIC2042 and MIC2043 are high-side MOSFET switches
optimized for general purpose power distribution applications
which require circuit protection. The devices switch up to 5.5V
and as low as 0.8V while offering both programmable current
limiting and thermal shutdown to protect the device and the
load. A fault status output is provided in order to detect
overcurrent and thermal shutdown fault conditions. Both
devices employ soft-start circuitry to minimize the inrush
current in applications that employ highly capacitive loads.
Additionally, for tighter control over inrush current during
start-up, the output slew-rate may be adjusted by an external
capacitor.

The MIC2043 features a auto-reset circuit breaker mode that
latches the output off upon detecting an overcurrent condition
lasting more than 28ms. The output is reset by removing or
reducing the load.

All support documentation can be found on Micrel's web
site at www.micrel.com.

Typical Application

8, 12

10,11,14

SET

200

Note:
All V

pins (8, 12) must be externally tied together.

All V

OUT

pins (10, 11, 14) must be externally tied together.

LIMIT

2A.

Output Power-Good = 3.0V.
*C4 is optional. See

"Applications Information."

C4*

0.022

0.1

Logic

Controller

ON/OFF

OVERCURRENT

MIC2042-1BTS

MIC39100-2.5BS

VBIAS

VIN

/FAULT

ILIM

SLEW

2.5V

VOUT

PGREF

PWRGD

UVLOIN

GND

+3.3V

Power

Supply

20k

294k

1%
R3

24.3k

GND

OUT

LOAD

(OPEN)

OUT

3.3V@ 1.5A

OUT1

OUT2

0.1

4.7

Features

· 60m

max. on-resistance

· 0.8V to 5.5V operating range
· Adjustable current limit
· Power-Good detection
· Up to 3A continuous output current
· Short-circuit protection with thermal shutdown
· Adjustable slew-rate control
· Circuit breaker mode (MIC2043)
· Fault status flag
· Undervoltage lockout
· Output MOSFET reverse current flow block when

disabled

· Very fast reaction to short-circuits
· Low quiescent current

Applications

· Docking stations
· Notebook PCs
· PDAs
· Hot swap board insertions
· RAID controllers
· USB hosts
· ACPI power distribution

Micrel, Inc. · 1849 Fortune Drive · San Jose, CA 95131 · USA · tel + 1 (408) 944-0800 · fax + 1 (408) 944-0970 · http://www.micrel.com

November 2003

M0512-112603

MIC2042/2043

Micrel

Pin Description

Pin Number

Pin Name

Pin Function

8-Pin SOP

14-Pin TSSOP

Switch Enable Input: Gate control pin of the output MOSFET available as an
active high (1) or active low (2) input signal.

/FAULT

Fault Status Output: Open-drain N-Channel device, active low. This pin
indicates an overcurrent or thermal shutdown condition. For an overcurrent
event, /FAULT is asserted if the duration of the overcurrent condition lasts
longer than 28ms.

GND

Ground Connection: Tie to analog ground.

N/A

SLEW

Slew-Rate Control Input: A capacitor connected between this pin and ground
will reduce (slow) the output slew-rate. The output turn-on time must be less
than the nominal flag delay of 28ms in order to avoid nuisance tripping of the
/FAULT output since V

OUT

must be "fully on" (i.e., within 200mV of the voltage

at the input) before the /FAULT signal delay elapses. The capacitor requires a
16V rating, or greater, 25V is recommended. See

"Applications Information,"

"Output Slew-Rate Adjustment" for further detail.

ILIM

Current Limit Set: A resistor, R

SET

, connected to this pin sets the current

limit threshold as CLF/R

SET

, where CLF is the current limit factor specified in

the

"Electrical Characteristics" table. For the MIC2042/43, the continuous

output current range is 0.5A to 3A.

5,7

8,12

VIN

Switch Input Supply: The drain of the output MOSFET. The range of input for
the switch is 0.8V to 5.5V. These pins must be externally connected together
to achieve rated performance.

6,8

10,11,14

VOUT

Switch Output: The source of the output MOSFET. These pins must be
externally connected together to achieve rated performance.

N/A

VBIAS

Bias Supply Input: This input pin supplies power to operate the switch and
internal circuitry. The input range for V

BIAS

is 1.6V to 5.5V. When switched

voltage (V

) is between 1.6V to 5.5V and the use of a single supply is desired,

connect VBIAS to VIN externally.

N/A

PGREF

Power-Good Threshold (Input): Analog reference used to specify the
PWRGD threshold. When the voltage at this pin exceeds its threshold, V

PWRGD is asserted high. An external resistive divider network is used to
determine the output voltage level at which V

is exceeded. See

"Functional Description" for further detail. When the PWRGD signal is not
utilized, this input should be tied to VOUT.

N/A

PWRGD

Power-Good Output: Active high, open-drain. This pin asserts high when the
voltage at PGREF exceeds its threshold.

N/A

UVLOIN

Undervoltage Lockout Adjust Input: With this pin left open, the UVLO
threshold is internally set to 1.45V. When the switching voltage (V

) is below

1.6V, connecting an external resistive divider to this input will lower the
UVLO threshold. The total resistance of the divider must be less than
200k

. See

"Applications Information" for further detail.

MIC2042/2043

Micrel

M0512-112603

November 2003

Electrical Characteristics

(4)

= V

BIAS

= 5V; T

= 25

C unless specified otherwise. Bold indicates 40

C to +85

Symbol

Parameter

Condition

Min

Typ

Max

Units

Switch Input Voltage

BIAS

14-pin TSSOP

0.8

5.5

8-pin SOP

1.6

5.5

BIAS

Bias Supply Voltage

(14-pin TSSOP)

1.6

5.5

BIAS

VBIAS Supply Current - Switch OFF

No load

0.1

VBIAS Supply Current - Switch ON

No load

300

400

Note 5

Enable Input Voltage

(max)

2.4

1.5

(min)

3.5

2.5

ENHYST

Enable Input Threshold Hysteresis

100

Enable Input Current

= 0V to 5.5V

.01

DS(ON)

Switch Resistance

= V

BIAS

= 3V, 5V

OUT

= 500mA

LEAK

Output Leakage Current

Output off

CLF

Current Limit Factor

(2)

= 5V, 0.5V

OUT

< 0.5V

310

395

485

0.5A

OUT

= 3V, 0.5V

OUT

< 0.5V

320

385

450

0.5A

OUT

PGREF and UVLOIN Threshold

= V

BIAS

= 1.6V to 5.5V

205

225

245

(14-pin TSSOP)

LATCH

Output Reset Threshold

= 0.8V to 5.5V

.0.2

OUT

rising (MIC2043)

LATCH

Latched Output Off Current

Output latched off (MIC2043)

Output Low Voltage

(/FAULT) = 15mA

0.4

(/FAULT, PWRGD)

(PWRGD) = 5mA

OFF

/FAULT, PWRGD Off Current

FAULT

= V

PWRGD

= 5V

Undervoltage Lockout Threshold

rising

1.30

1.45

1.58

falling

1.20

1.35

1.50

UVHYST

Undervoltage Lockout

100

Threshold Hysteresis

UVINTH

UVLO Adjust Pin Threshold Voltage

rising

205

225

245

falling

185

205

225

UVINHYST

UVLO Adjust Pin Threshold Hysteresis

Overtemperature Threshold

increasing

140

decreasing

120

Absolute Maximum Ratings

(1)

Supply Voltage

and V

BIAS .............................................................................

/FAULT, PWRGD Output Voltage ................................... 6V

/FAULT, PWRGD Output Current .............................. 25mA

Junction Temperature (T

) ...................... Internally Limited

ESD Rating

(3)

Human Body Model ................................................... 3kV
Machine Model ........................................................ 200V

Operating Ratings

(2)

Supply Voltage

............................................................... 0.8V to 5.5V

BIAS

........................................................... 1.6V to 5.5V

Continuous Output Current ................................ 0.5A to 3A

Ambient Temperature (T

) ........................... 40

C to 85

Package Thermal Resistance

SOP (

) .......................................................... 160

C/W

TSSOP (

) ....................................................... 85

C/W

November 2003

M0512-112603

MIC2042/2043

Micrel

Symbol

Parameter

Condition

Min

Typ

Max

Units

FLAG

Flag Response Delay

= V

BIAS

= 3V, 5V

Output Turn-on Delay

LOAD

= 10

, C

LOAD

= 1

600

800

1000

Output Turn-on Rise Time

LOAD

= 10

, C

LOAD

= 1

1.5

OFF

Output Turn-off Delay

LOAD

= 10

, C

LOAD

= 1

Output Turn-off Fall Time

LOAD

= 10

, C

LOAD

= 1

Notes:

Exceeding the absolute maximum rating may damage the device.

The device is not guaranteed to function outside its operating rating.

Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.

Specification for packaged product only.

OFF is V

< 1.0V for MIC2042/MIC2043-1 and V

> 4.0V for MIC2042/MIC2043-2. ON is V

> 4.0V for MIC2042/MIC2043-1 and V

< 1.0V for

MIC2042/MIC2043-2.

The current limit is determined as follows: I

LIM

= CLF/R

SET

Timing Diagrams

50%

(a) MIC2042/43-1

(b) MIC2042/43-2

10%

90%

OFF

OUT

50%

10%

90%

OFF

OUT

Figure 1. Turn-On/Turn-Off Delay

LIMIT

OUT

/FAULT

FLAG

0.2V

Increase the load

Figure 2. Overcurrent Fault Response -- MIC2042-2

November 2003

M0512-112603

MIC2042/2043

Micrel

Typical Characteristics

100

150

200

250

300

350

400

450

500

-40 -20

80 100

SUPPLY CURRENT (

TEMPERATURE (

Supply Current

vs. Temperature

= V

BIAS

= 1.6V

= V

BIAS

= 5.5V

= V

BIAS

= 3V

0.5

1.5

2.5

3.5

-40 -20

80 100

(V)

TEMPERATURE (

Enable Input Threshold

(Falling)

vs. Temperature

BIAS

= 5.5V

BIAS

= 3V

BIAS

= 1.6V

0.5

1.5

2.5

3.5

-40 -20

80 100

(V)

TEMPERATURE (

Enable Input Threshold

(Rising)

vs. Temperature

BIAS

= 5.5V

BIAS

= 3V

BIAS

= 1.6V

100

200

300

400

500

600

-40 -20

80 100

OUTPUT LEAKAGE (nA)

TEMPERATURE (

Output Leakage Current

vs. Temperature

BIAS

= 5.5V

BIAS

= 3V

BIAS

= 1.6V

210

215

220

225

230

-40 -20

80 100

(mV)

TEMPERATURE (

Power-Good Reference

Threshold

vs. Temperature

@ 1.6V to 5.5V

1.2

1.25

1.3

1.35

1.4

1.45

1.5

1.55

-40 -20

80 100

UVLO (V)

TEMPERATURE (

UVLO Threshold

vs. Temperature

UVLO+

UVLO

200

205

210

215

220

225

230

235

240

245

250

-40 -20

80 100

UVLO (V)

TEMPERATURE (

UVLO Adjust PinThreshold

vs. Temperature

UVLO+

UVLO

-40 -20

80 100

RDS(ON)

TEMPERATURE (

On Resistance

vs. Temperature

= V

BIAS

= 5V

= V

BIAS

= 3V

= V

BIAS

= 1.6V

-40 -20

80 100

FLAG

(ms)

TEMPERATURE (

Flag Response Delay

vs. Temperature

FLAG

= 3V

FLAG

= 5V

500

550

600

650

700

750

800

850

900

-40 -20

80 100

TURN ON DELAY (

TEMPERATURE (

Turn-On Delay

vs. Temperature

= V

BIAS

= 5.5V

= V

BIAS

= 3V

= V

BIAS

= 1.6V

2 2.5 3 3.5 4 4.5 5 5.5 6

(mA)

OUT

(V)

BIAS

Reverse Current Flow

vs. Output Voltage

= GND

BIAS

= 1.6V

-40 -20

80 100

SLEW VOLTAGE (V)

TEMPERATURE (

Slew Voltage

vs. Temperature

= V

BIAS

= 5V

= V

BIAS

= 3V

= V

BIAS

= 1.6V

November 2003

M0512-112603

MIC2042/2043

Micrel

Functional Description

The MIC2042 and MIC2043 are high-side N-Channel switches
equipped with programmable current limit up to 3A for use in
general purpose power distribution applications. The switches,
available with active-high or active-low enable inputs, provide
output slew-rate control and circuit protection via thermal
shutdown and an optional output latch during overcurrent
conditions.

Input and Output

BIAS

supplies power to the internal circuitry of the switch and

must be present for the switch to operate. V

is connected to

the drain of the output MOSFET and sources power to the
switched load. V

must be less than or equal to V

BIAS

. V

OUT

is the source terminal of the output MOSFET and attaches to
the load. In a typical circuit, current flows from V

to V

OUT

toward the load. If V

OUT

is greater than V

, current will flow

from V

OUT

to V

since the switch is bi-directional when the

device is enabled. When disabled (OFF), the switch will block
current flow from either direction.

Enable Input

Enable, the ON/OFF control for the output switch, is a digital
input available as an active-high (1) or active-low (2)
signal. The EN pin, referenced to approximately 0.5

VBIAS,

must be driven to a clearly defined logic high or logic low.
Failure to observe this requirement, or allowing EN to float,
will cause the MIC2042/43 to exhibit unpredictable behavior.
EN should not be allowed to go negative with respect to
ground, nor allowed to exceed VBIAS. Failure to adhere to
these conditions may result in damage to the device.

Undervoltage Lockout

When the switch is enabled, undervoltage lockout (UVLO)
monitors the input voltage, V

, and prevents the output

MOSFET from turning on until V

exceeds a predetermined

level, nominally set at 1.45V. The UVLO threshold is adjust-
able and can be varied by applying an external resistor divider
to the UVLOIN pin from VIN to GND. The resistive divider
network is required when the input voltage is below 1.5V. The
UVLO threshold is internally preset to 1.45V if the UVLOIN
pin is left open. See

"Applications Information" section.

Programmable Current Limit

The MIC2042/43 is designed to prevent damage to the
external load by limiting the maximum amount of current it
can draw. The current limit is programmed by an external
resistor (R

SET

) connected from ILIM to ground and becomes

active when the output voltage is at least 200mV below the
voltage at the input to the device. The limiting current value
is defined by the current limit factor (CLF) divided by R

SET

and the MIC2042/43 will limit from 0.5A to 3A with a set point
accuracy of

22%. In programming the nominal current limit,

the value of R

SET

is determined using the following equation:

CLF

390A

SET

LIMIT

(

)

(1)

And given the

22% tolerance of the current limit factor (CLF),

the external resistor is bound by:

103

SET

970

(2)

The graphs below (Figure 3) display the current limit factor
characteristic over the full temperature range at the indicated
voltage. These curves can be used as a point of reference in
determining the maximum variation in the device's current
limit over the full temperature range. For example: With
V

= V

BIAS

= 3.0V and a nominal 2A current limit

SET

= 192

), the low and high current limit settings for the

MIC2042/43 would be 1.66A and 2.34A, respectively, as
shown on the 3V graph using the 192

reference point.

When current limiting occurs, the MIC2042 and MIC2043
respond differently. Upon first reaching the limiting current
both devices restrict current flow, allowing the load voltage to
drop below V

. If the VIN-to-VOUT differential voltage ex-

ceeds 200mV, then a fault condition is declared and the fault
delay timer is started. If the fault condition persists longer than
the delay period, typically 28ms, then the /FAULT output
asserts low. At this point, the MIC2042 will continue to supply
current to the load at the limiting value (I

LIMIT

), whereas the

MIC2043 will latch off its output.

0.5

1.5

2.5

3.5

0 120 240 360 480 600 720 840 960

LIM

(A)

SET

(

)

Current Limit

vs. R

SET

C to +85

= V

BIAS

= 5V

CLF (LO)

CLF (HI)

0.5

1.5

2.5

3.5

0 120 240 360 480 600 720 840 960

LIM

(A)

SET

(

)

Current Limit

vs. R

SET

C to +85

= V

BIAS

= 3V

CLF (LO)

CLF (HI)

0.5

1.5

2.5

3.5

0 120 240 360 480 600 720 840 960

LIM

(A)

SET

(

)

Current Limit

vs. R

SET

C to +85

= V

BIAS

= 1.6V

CLF (LO)

CLF (HI)

Figure 3. Current Limit Factor

MIC2042/2043

Micrel

M0512-112603

November 2003

/FAULT

The /FAULT signal is an N-Channel, open-drain MOSFET
output. An external pull-up resistor tied to a maximum 6V rail
is required for the /FAULT pin. The /FAULT pin is asserted
(active-low) when either an overcurrent or thermal shutdown
condition occurs. During a hot insert of a PCB or when turning
on into a highly capacitive load, the resulting high transient
inrush current may exceed the current limit threshold of the
MIC2042/43. In the case where an overcurrent condition
occurs, /FAULT will assert only after the flag delay time has
elapsed, typically 28ms. This ensures that /FAULT is as-
serted only upon valid overcurrent conditions and that nui-
sance error reporting is prevented.

Thermal Shutdown

For the MIC2042, thermal shutdown is employed to protect
the device from damage should the die temperature exceed
safe margins due to a short circuit or an excessive load.
Thermal shutdown shuts off the output MOSFET and asserts
the /FAULT output if the die temperature exceeds 140

C. The

MIC2042 automatically resets its output and resumes supply-
ing current to the load when the die temperature drops to
120

C. If the fault is still present, the MIC2042 will quickly re-

heat and shut down again. This process of turning
ON-OFF-ON is called thermal cycling and will continue as
long as the power switch is enabled while the fault or
excessive load is present.

Depending on PCB layout (including thermal considerations
such as heat sinking), package, and ambient temperature, it
may take several hundred milliseconds from the incidence of
the fault to the output MOSFET being shut off.

Circuit Breaker Function (MIC2043)

The MIC2043 is designed to shut off all power to the load
when a fault condition occurs, just as a circuit breaker would
do. A fault condition is deemed to be anytime the output
current exceeds the current limit for more than the flag delay
period, nominally 28ms. Once the output shuts off, it remains

off until either the fault load is removed from VOUT or the EN
input is cycled ON-OFF-ON. If the fault is still present after EN
has been cycled, the MIC2043 will again shut off all power to
the load after 28ms. Once the fault has been removed, then
normal operation will resume.

Open Load Detection

The MIC2043 will automatically reset its output when the fault
load is cleared. This is accomplished by applying a small
current to VOUT and watching for the voltage at VOUT to rise
to within 200mV of VIN. This current is supplied by an internal
resistor connected to VIN and is connected to VOUT when
MIC2043 latches off.

Power-Good Detection

The MIC2042/43 can detect when the output voltage is above
or below a preset threshold that is monitored by a comparator
at the PGREF input. The PWRGD signal is an N-Channel
open-drain MOSFET output and an external pull-up resistor
up to a 6V maximum rail is required for the PWRGD pin.
Whenever the voltage at the PGREF pin exceeds its thresh-
old (V

), typically 230mV, the PWRGD output is asserted.

Using the typical applications circuit from page 1 that switches
3.3V as an example, the output voltage threshold determin-
ing "power is good" is calculated by the following equation:

OUT(GOOD)

× +

(3)

In substituting the resistor values of the circuit and the typical
PGREF threshold, the resulting V

OUT(GOOD)

is calculated as

3.0V for this 3.3V switching application.

Slew

The MIC2042/43's output rise time is controlled at turn-on to
a minimum of 1.5ms and is controlled by an internal slew-rate
limiting circuit. A slew-rate adjustment control pin is available
for applications requiring slower rise times. By placing a
capacitor between SLEW and ground, longer rise times can
be achieved. For further detail, see the

"Applications Informa-

tion" section.

November 2003

M0512-112603

MIC2042/2043

Micrel

Applications Information

Input and Output

Supply Bypass Filtering

The need for input supply bypass is necessary due to several
factors, most notably the input/output inductance along the
power path, operating current and current limit, and output
capacitance. A 0.1

F to 0.47

F bypass capacitor positioned

very close to the VIN pin to GND of the device is strongly
recommended to filter high frequency oscillations due to
inductance. Also, a sufficient bypass capacitor positioned
close to the input source to the switch is strongly advised in
order to suppress supply transient spikes and to limit input
voltage droop. Inrush current increases with larger output
capacitance, thus the minimum value of this capacitor will
require experimental determination for the intended applica-
tion and design. A good starting point is a capacitor between
4.7

F to 15

F. Without these bypass capacitors, an extreme

overload condition such as a short circuit, or a large capaci-
tive load, may cause either the input supply to exceed the
maximum rating of 6V and possibly cause damage to the
internal control circuitry or allow the input supply to droop and
fall out of regulation and/or below the minimum operating
voltage of the device.

Output Capacitance

When the MIC2042 die exceeds the overtemperature thresh-
old of approximately 140

C, the device can enter into a

thermal shutdown mode if the die temperature falls below
120

C and then rises above 140

C in a continuous cycle.

With the VOUT and /FAULT outputs cycling on and off, the
MIC2042 will reset the /FAULT while in an overtemperature
fault condition if the output voltage is allowed to swing below
ground. The inductance present at the output must be neu-
tralized by capacitance in order to ensure that the output does
not fall below ground. In order to counter the board parasitic
inductance and the inductance of relatively short-length
power cable (

1ft., 16 to 20 gauge wire), a minimum output

capacitance of 22

F is strongly recommended and should be

placed close to the VOUT pin of the MIC2042. For applica-
tions that use more than a foot of cable, an additional
10

F/ft. is recommended.

Reverse Current Block

The MIC2042/43 provides reverse current flow block through
the output MOSFET if the voltage at VOUT is greater than VIN
when the device is disabled. The VBIAS supply pin has a
limited reverse current flow if the voltage at VOUT is pulled
above VBIAS when the device is disabled. A graph of the
V

BIAS

reverse current flow is shown in the

"Functional Char-

acteristics" plots. The reverse current for V

BIAS

can be

completely blocked by inserting a Schottky diode from the
VBIAS pin (cathode) to the supply (anode). However, the
minimum voltage of 1.6V must be supplied to VBIAS after
accounting for the voltage drop across the diode.

Output Slew-Rate Adjustment

The output slew-rate for the MIC2042/43 can be slowed down
by the capacitor (16V rating, minimum; 25V suggested)
between SLEW and GND. The slew-rate control circuitry is
independent of the load capacitance and exhibits a non-

linear response. See the

"Functional Characteristics" plots.

Table 1 shows the rise time for various standard capacitor
values. Additionally, the output turn-on time must be less than
the nominal flag delay of 28ms in order to avoid nuisance
tripping of the /FAULT output. This limit is imposed by the
current limiting circuitry which monitors the (VIN VOUT)
differential voltage and concludes a fault condition is present
if the differential voltage exceeds 200mV for more than the
flag delay period. For the MIC2043, the /FAULT will assert
and the output will latch off if the output is not within 200mV
of the input before the flag delay times out. When using the
active-low (2) option with the EN input tied to ground, slew
control is functional during initial start-up but does not func-
tion upon resetting the input power to the device. In order for
the SLEW control to operate during consecutive system
restarts, the EN pin must reset (toggle OFF to ON).

UVLO Threshold Setting With Low Input Voltages

When the switching voltage is below 1.6V, the device's
standard UVLO threshold (1.45V nominal) will hinder the
output MOSFET in switching VIN to VOUT. In this case, the
use of the UVLOIN pin is required to override the standard
UVLO threshold and set a new, lower threshold for the lower
input voltage. An external resistive divider network con-
nected at the UVLOIN pin is used to set the new threshold.
Due to the ratio of the internal components, the total series
resistance of the external resistive divider should not exceed
200k

. The circuit shown in Figure 4 illustrates an application

that switches 0.8V while the device is powered from a
separate 2.5V power supply. The UVLO threshold is set by
the following equation:

0.23V

UVTH

× +

(4)

In substituting the resistor values from Figure 4, the resulting
UVLO threshold (V

UVTH

) is calculated as 0.6V for this 0.8V

switching application. When using the UVLOIN pin to set a
new UVLO threshold, an optional 0.1

F to 1.0

F capacitor

from UVLOIN to GND may be used as a glitch filter in order
to avoid nuisance tripping of the UVLO threshold. If the
UVLOIN pin is not in use, this pin should be left open
(floating). The use of a pull-down resistor to ground will offset
the ratio of the internal resistive divider to this pin resulting in
a shift in the UVLO threshold. To bypass (disable) UVLO,
connect the UVLOIN pin directly to the VIN pin of the
MIC2042/43.

Conditions: V

= V

BIAS

= 5V/3V; C

LOAD

= 47

F; I

LOAD

= 1A

SLEW

(

Rise Time (ms)

0.01

4.75

0.033

10.5

0.047

0.1

Table 1. Typical Output Rise Time for Various C

SLEW

MIC2042/2043

Micrel

M0512-112603

November 2003

Power Dissipation

Power dissipation depends on several factors such as the
load, PCB layout, ambient temperature, and package type.
The following equations can be used to calculate power
dissipation and die temperature.

Calculation of power dissipation can be accomplished by the
following equation:

= R

DS(ON)

OUT

)

(5)

To relate this to junction temperature, the following equation
can be used:

= P

+ T

(6)

where T

= junction temperature, T

= ambient temperature

and R

is the thermal resistance of the package.

Printed Circuit Board Hot-Plug

The MIC2042/43 are ideal inrush current limiting power
switches suitable for hot-plug applications. Due to the inte-
grated charge pump, the MIC2042/43 present a high imped-
ance when in the off state and the device slowly becomes a
low impedance as it turns on. This effectively isolates power
supplies from highly capacitive loads by reducing inrush
current during hot-plug events. This same feature also can be
used for soft-start requirements.

PCB Layout Recommendations

The MIC2042 and MIC2043 have very low on-resistance,
typically 40m

, and the switches can provide up to 3A of

continuous output current. Under such heavy loads, the
power consumed by the devices may cause the devices to

8, 12

10,11,14

SET

200W

0.1mF

MIC2042-1BTS

VBIAS

VIN

/FAULT

UVLOIN

SLEW

VOUT

PGREF

PWRGD

ILIM

GND

47kW

75kW

1%
R5

36.5kW

LOAD

22mF

OUT

0.8V @1.5A

47kW

Digital

Output

Signals

10mF

0.1mF

0.8V

2.5V

95.3kW

59kW

47kW

Note:

All V

pins (8, 12) must be externally tied together.

All V

OUT

pins (10, 11, 14) must be externally tied together.

Undervoltage Lockout = 0.6V.

Output Power-Good = 0.7V.

Figure 4. Lower UVLO Setting

heat up considerably. The following list contains some useful
suggestions for PCB layout design of the MIC2042/43 in
order to prevent the die from overheating under normal
operating conditions:

1. Supply additional copper area under the device to

remove heat away from the IC.

See

"Application Hint 17" for a general guideline in

calculating the suggested area.

2. Provide additional pad area on the corner pins of the

MIC2042/43 IC for heat distribution.

3. Tie the common power pins (VIN = pins 8 and 12 and

VOUT = pins 10, 11, 14 for the 14-pin TSSOP, VIN =
pins 5 and 7 and VOUT = pins 6 and 8 for the 8-pin
SOP) together in a manner such that the traces
entering and leaving the device have a uniform width
sufficient for the application's current requirements
plus added margin (25% minimum recommended).

Ex: For 2A maximum current, design traces for
2.5A capability.

4. For PCB trace width calculation, there are numerous

calculator programs available on the internet and
elsewhere. As a general rule of thumb, 15-20 mils for
every 1A of current when using 1oz. copper. However,
the trace width calculators often take into account
maximum temperature increase constraints, as well
as layer arrangement, in determining the PCB trace
widths.

November 2003

M0512-112603

MIC2042/2043

Micrel

Package Information

0.244 (6.20)
0.228 (5.79)

0.197 (5.0)
0.189 (4.8)

SEATING

PLANE

0.026 (0.65)

MAX

)

0.010 (0.25)
0.007 (0.18)

0.064 (1.63)
0.045 (1.14)

0.0098 (0.249)
0.0040 (0.102)

0.020 (0.51)
0.013 (0.33)

0.157 (3.99)
0.150 (3.81)

0.050 (1.27)

TYP

PIN 1

DIMENSIONS:

INCHES (MM)

0.050 (1.27)
0.016 (0.40)

8-Pin SOP (M)

1.10 MAX (0.043)

0.15 (0.006)
0.05 (0.002)

1.00 (0.039) REF

0.65 BSC
(0.026)

6.4 BSC (0.252)

5.10 (0.200)
4.90 (0.193)

0.20 (0.008)
0.09 (0.003)

0.70 (0.028)
0.50 (0.020)

DIMENSIONS:

MM (INCH)

4.50 (0.177)
4.30 (0.169)

0.30 (0.012)
0.19 (0.007)

14-Pin TSSOP (TS)

MICREL, INC.

1849 FORTUNE DRIVE

SAN JOSE, CA 95131

USA

TEL

+ 1 (408) 944-0800

FAX

+ 1 (408) 944-0970

WEB

http://www.micrel.com

The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use.

Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.

Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can

reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's

use or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser's own risk and Purchaser agrees to fully indemnify

Micrel for any damages resulting from such use or sale.

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: MIC2043

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: MIC2043